[PATCH v8 14/14] ARM: gic: add gic_ppi_map_on_cpu()

[Russell King - ARM Linux]

On Mon, Jul 11, 2011 at 12:14:36PM +0100, Marc Zyngier wrote:
> And that's exactly what it does:
> http://www.mail-archive.com/devicetree-discuss@lists.ozlabs.org/msg05026.html
> 
> What I was trying to explain (and obviously failed to) is that the
> _Linux_ DT _code_ will try to resolve the PPI number and convert it to a
> _Linux_ IRQ number. Unless of course you don't encode it as an interrupt
> at all, which seems to be what you're aiming for.

I'm not aiming for anything.  I'm trying to get you to fully understand
the issue I've raised with your patches.  So, let's try a new scenario
based on your statement above.

You have a device which happens to use a PPI.  You obtain its IRQ number
from DT, which tells you IRQ 9, because the DT information said PPI 2
CPU 1.  So you pass IRQ 9 into the IRQ request function, but as you're
running on CPU 3, you have no access to the hardware for IRQ 9.

Please describe in detail how, with your patches, PPI 2 CPU 1 gets enabled
rather than PPI 2 CPU 3 when IRQ 9 is requested.